I have to replace a couple of rivets on the skin of my right elevator. They were back riveted to the rib halves and I didn't realize that the top of the workbench wasn't solid enough for the task and they didn't set into the dimple properly. They were originally 426AD3-3. I had already replaced one of them but had done a poor job drilling it out so I replaced it with a 426AD4-4. I'll be replacing the 3-3 with an MK319-BS but what should I use to replace the 4-4? CS-4?